Service provider networks typically deliver services, such as digital television, high-speed Internet, Voice-over-IP (VoIP), etc., to customer premises. Service provider networks, including cable networks, have, in recent years, moved beyond merely broadcasting television signals over a coaxial cable to subscribers in their homes. The networks typically carry bi-directional traffic. For example, in addition to receiving data and broadcasts, subscribers of a cable network have a modem allowing the transmission of digital signals upstream toward a headend of the network. Among many services afforded by cable modems are Internet services, voice-over-Internet-Protocol (VoIP) phone services, etc.
Noise in a cable transmission system has always been problematic. For example, in a cable television (CATV) upstream communication system, where signals are transmitted upstream from the customer premise to the headend, a carrier-to-noise ratio (CNR) or a signal-to-noise ratio (SNR) can be used as a measure of signal integrity to identify an existing problem, like ingress noise, in the upstream channel. However, a CNR or SNR value itself does not readily identify the root cause for noise or interference in the signal.